1. Field of the Invention
The present invention relates to a process for preparing perfluoroalkylanilines and to their use for preparing active ingredients, in particular for agrochemicals.
2. Brief Description of the Prior Art
Perfluoroalkylanilines, in particular 4-perfluoroalkyl-2-methylanilines, are valuable starting materials for preparing insecticides of the aroylurea type (see also EP-A 919 542 and EP-A 936 212). Perfluoroalkylanilines can be prepared, for example, by reacting anilines with perfluoroalkyl iodides or bromides in aprotic solvents, either in the presence of metals and sulphur dioxide (EP-A 206 951 and FR-A 2 660 923) or in the presence of alkali metal dithionite (EP-A 298 803). In a similar manner, perfluoroalkyl chlorides can be reacted in dimethyl sulphoxide (Huang et al., J. Fluorine Chem., 111, 2001, 107–113). A disadvantage of the methods mentioned is that the perfluoroalkyl iodides or bromides are very expensive and only allow very low or only moderate yields to be achieved.
EP-A 1 006 102 discloses that perfluoroalkylanilines can be obtained by reacting anilines with perfluoroalkyl iodides in a biphasic system in the presence of a reducing agent. However, in this case also, the high cost of the perfluoroalkyl iodides is disadvantageous.
There is therefore a need to provide a process which enables the preparation of perfluoroalkylanilines in good yields and in a simple manner.